Configuring Persona in Outlook with ZCO 6.0.4 does nothing

I'm trying hard to change From address to some alias in Outlook 2007, without any luck so far.

Changed Personas (Tools->Options->Personas->DEFAULT; Choose what appears in the FROM field...), added new Personas, changed in account on Zimbra side where ever I could find it (account name, Preferences->Accounts->Add Persona)...

Works from Web client, but Outlook doesn't want to cooperate at all. It is caching the old value somewhere, and drives me nuts. Also drives one of our big customers nuts.

Is that a bug in ZCO? Or there is some super-secret file where I can change it?